Frosted lamp



F. KALLUS IFROSTED LAMP April 21, 1942.,

Filed 0ct.- 6, 1939 3 00 m MK M E w e F ATTORNEYS Patented Apr. 21, 1942UNITED STATES OFFICE FROSTED LAMP Frederick Kallus, Hoboken, N. J.

Application October 6, 1939, Serial No. 298,202

4 Claims.

describe an improved method for frosting lamp bulbs utilizing a dilutesolution of etching fluid in conjunction with a subsequent treatment ofthe etched surface by means of steam. Glass,v

particularly the thin glass of electric light bulbs, when etched isweakened structurally and becomes brittle unless there is somesubsequent treatment having the effect of annealing or tempering. Insome cases this is accomplished by a second treatment with a solution ofthe etching fluid more dilute than that used in the first treatment. Asdescribed in my patent, steam accomplishes a similar result in somemanner not clearly understood by relieving the strain of the glassmaterial and eliminating the fragility.

An object of the invention is'to produce a frosted lamp bulb in which ahigh degree of rigidity of the etched surface is obtained.

An object also is the production of a frosted lamp bulb surface in whichthe glass material assumes in section an undulating contour.

Additional objects relate to the production of an etched surfacecontaining pseudo-crystalline polyhedrcns; having a striated fractureadjacent I the surface; and possessing pronounced resistance tofracture.

Other objects will appear on consideration of the following descriptionof the process and product, and of the accompanying drawing, in which:

Fig. 1 is a lamp bulb to which my invention is applied Fig. 2 is aphotomicrograph of a glass surface etched in accordance with my process;and

Fig. 3 is a transverse section through a glass surface etched accordingto my process.

In my co-pending application Serial No. 400,381, filed June 30, 1941, Ihave described a process for making frosted lamps which employs steam ata temperature preferably below 450 C. as an annealing agent after theetching been completed.

The lamp bulbs frosted in accordance with my process are found to havespecial characteristics arising from the nature of the etched surface.Etching, since it removes material, ordinarily step has weakens theglass, this being due primarily to sharp angle crevices on the glasssurface forming a line of weakness inducing fragility. Various meanshave been suggested for overcoming this fragile condition, such as asecond treatment of etching fluid diluted to reduce the speed of action,and other means. In my process I overcome the fragile characteristic ofthe glass by the use of steam immediately after the etching bath, thusstopping the etching action and producing a modified preliminaryannealing of the surface subjected to strain. The final annealing stepcompletely removes any strain distortions and rounds out all angularcrevices so that ample strength is imparted to the glass wall to permithandling and use as electric lamp bulbs;

In Figs. 2 and 3 are illustrated photomicrographs of the etched surfaceof glass frosted in accordance with my method. It is pointed out thatthe surface is crystalline in appearance, there being largeprotuberances of a polyhedral or pyramidal type having usually four orsix sides with the area intermediate the protuberances taken up by smallprotuberances, the amount of unformed material being practicallynegligible. A section taken'through this material, as indicated in Fig.3, shows an undulating line and also shows that the glass has striationsor grains, the

same being normal to the surface tangent. These characteristics are suchas to distinguish a product of maximum strength and high refractabilityfor light, so that electric lamps manufactured'from these bulbs diffuselight with superior efficiency. This may be apparent when it isconsidered that the light beams are refracted not only by the prism-1ikeprojections of the etched surface but also by the striated sub-stratumadjacent this surface.

Modifications of the invention may be made and hence I do not desire tobe restricted in the scope of my invention other than may be, determinedby the claims hereto appended.

I claim as my invention:

1. A glass lamp bulb having an etched interior surface formed ofmultiple, irregularly shaped, fissure-separated masses of differentsizes wheres fissure-separated masses of different sizes wherer by theglass surface is roughened, the glass be-.

neath the surface having a plurality of striations extendingsubstantially normal to the tangent curvature of said surface, thelength of said striations exceeding the maximum depth of said Ifissures.

3. A glass lamp bulb having a roughened interior surface, the glassbeneath said surface being striated.

FREDERICK KALLUS.

